The aeronautical navigation maps that flag the risks of collision with the ground normally comprise a summary image of the region being flown over similar to a contour map in which the relief being flown over is shown by overlaid slices, assigned false colors and/or different textures and/or symbols giving them an appearance that is all the more eye-catching as the risk of collision increases. Some more detailed maps also show the background relief. Their generation implies an estimation of the risk of ground collision presented by each point of the relief of the represented region being flown over.
The estimation of the risk of ground collision presented by each point of the relief of the represented region being flown over can be carried out by a simple comparison of the elevations of the points of the region being flown over with a reference altitude which can be the current altitude of the aircraft or an altitude that can be predicted in the short or medium term for the aircraft. The displayed map then shows the relief by means of level sections staggered and referenced relative to that reference altitude.
The estimation of the risk of ground collision presented by each point of the represented region being flown over can also be carried out by looking to see if its overflight is within range of the aircraft taking into account an imposed vertical flight profile, that is, if there is a practicable path that avoids the prohibited zones, that observes the imposed vertical profile and a safe height relative to the relief being flown over, and that brings the aircraft from its current position to the point concerned. This search can be done implicitly by means of a method of estimating curvilinear distances for moving craft subject to static and dynamic route constraints such as that described by the Applicant in the French patent application filed on Sep. 26, 2003 under No. 0311320.
The currently known aeronautical navigation maps that flag the risks of ground collision have the drawback of assigning ground collision risk gradings to the zones of the region being flown over: high, medium, low, with no direct and intuitive relation for the pilot with a vertical speed set point.